Some machines such as, automobiles, trucks, vans, agriculture equipment, construction equipment, or the like, may be equipped with a multi-mode clutch actuation device. Moreover, such machines may include an internal combustion engine containing a rotatable crankshaft configured to transfer power from the engine through a driveshaft in order to propel the machine. Furthermore, a transmission may be positioned between the internal combustion engine and the driveshaft to selectively control torque and speed ratios between the crankshaft and driveshaft.
In the case of a manually operated transmission, a manually operated clutch may be positioned between the internal combustion engine and the transmission to selectively engage and disengage the crankshaft from the driveshaft in order to facilitate shifting through the available transmission gear ratios. Alternatively, in an automatically operated transmission, a plurality of automatically actuated clutch units may be adapted to dynamically shift through the available gear ratios without requiring operator intervention. In some embodiments, the plurality of clutch units or clutch modules may be incorporated within automatic transmissions to facilitate the automatic shifting through the gear ratios.
Moreover, the transmission may incorporate numerous sets of gears and the various gears may be structurally comprised of sun gears, intermediate gears, such as planet or pinion gears supported by carriers, and outer ring gears. Moreover, specific transmission clutches may be associated with specific sets of the selectable gears within the transmission to facilitate the desired ratio changes.
An exemplary automatic transmission clutch module that is associated with first (low) and reverse gear ratios may be positioned near the front of the transmission and closely adjacent to the engine crankshaft. The clutch may have a driving member and a driven member disposed circumferentially about the driving member. Furthermore, the driving and driven members may be configured to operate in multiple modes. In one non-limiting example, the driving member may be drivingly rotatable in only one direction. Alternatively or additionally, the driving member may be drivingly rotatable in a plurality of directions; however other modes and rotations may be possible. Moreover, the driving member may be selectively locked to the driven member via an engagement mechanism such as a roller, a sprag, a pawl or other known engagement mechanisms. The rotation of the driving member may be effective to directly transfer rotational motion from the engine to the driveline.
In some transmission systems, the driven member may be fixed to an internal case or housing of an associated planetary member of the automatic transmission. Under such circumstances, in a first configurational mode the driving member may need to be adapted to drive in one rotational direction, but freewheel in the opposite direction, in a condition referred to as overrunning. Those skilled in the art will appreciate that overrunning may be particularly desirable under certain operating states, such as when a machine is traveling downhill or coasting. Under such condition, the driven member may occasionally have a tendency to rotate faster than its associated driving member. Allowing the driving member to overrun the driven member may help provide protection against damage to the engine and/or transmission components.
In a second non-limiting mode, such as when a machine may be in reverse gear, the engagement mechanisms may be adapted for actively engaging in both rotational directions of the driving member, thus not allowing for an overrunning condition in either direction.
Automatic transmissions may include a plurality of gear sets to accommodate multiple gear ratios, and therefore the reliability of actuators used for automatically switching clutch modules between and/or among various available operating modes is a consistent design concern. As a result, much effort has been directed to finding ways to assure actuator reliability at competitive costs.